The collection of documents provides comprehensive guidance and analysis on the energy efficiency and environmental sustainability of data centres, covering both design and operation. One document presents the 2024 Best Practice Guidelines for the EU Code of Conduct on Data Centre Energy Efficiency, outlining detailed strategies for various aspects such as IT equipment, cooling, power, and monitoring metrics like PUE, ERE, WUE, and CUE. Other sources focus on best practices for energy-efficient data centre design, emphasising key steps for sustainability, including optimising cooling, power supplies, and air management using standards like ASHRAE and certifications like LEED. Additionally, two papers specifically examine the role of liquid cooling technology, such as immersion cooling, in reducing PUE and enabling waste heat recovery, while another paper performs a Life Cycle Assessment (LCA) of AI data centres to quantify carbon footprints and assess the impact of electricity mix and server lifespan extension. Collectively, the sources highlight the critical role of standardised metrics, efficient technology deployment, and holistic lifecycle thinking in achieving sustainable data centre operations globally.